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  • The time-dependent bulk response of poly (Methyl Methacrylate)
    Sane, S. B. ; Knauss, Wolfgang G.
    The dynamic bulk compliance of Poly (Methyl Methacrylate) (PMMA) has been determined at atmospheric pressure over a wide range of temperatures and frequencies, following a new examination of the bulk ... response of Poly (Vinyl Acetate) (PVAc) at different pressures. The overall bulk behavior of the current measurements of PVAc agrees fairly well with those reported by Deng and Knauss (1997) at atmospheric pressure, but a discrepancy in primarily the frequency response of the storage compliance is accredited to a difference in the moisture contents of the specimens. In PMMA, strong evidence of effects of physical aging on the volumetric behavior is observed and a careful prescription of thermal history was thus necessary to obtain consistent results. The master curves for the bulk compliance are generated by means of the time-temperature superposition principle. A comparison of the bulk and shear response shows that the extent of the transition ranges for the two material functions are comparable. Further comparison of the shift factors forbulk and shear responses supports the idea that different molecular mechanisms contribute to shear and bulk deformations. Another key observation regards the time-temperature superposition principle when applied to bulk compliance data of PMMA. The shifting procedure appears to lead to consistent results for temperatures below 92°, however its validity may have to be questioned for higher temperatures. This failure is tentatively attributed to the presence of primary \alpha and secondary \beta relaxation mechanisms with the latter possibly playing a dominant role in controlling the bulk deformations in the lower temperature range.
    Source: Mechanics of time-dependent materials : an international journal devoted to the time-dependent behaviour of materials and structures. - ISSN 1385-2000 (Vol. 5, no. 4, 2001, 293-324)
    Type of material - article, component part
    Publish date - 2001
    Language - english
    COBISS.SI-ID - 4853787

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